>>>>>> +static int jz4740_dma_alloc_chan_resources(struct dma_chan *c)
>>>>>> +{
>>>>>> + struct jz4740_dmaengine_chan *chan = to_jz4740_dma_chan(c);
>>>>>> +
>>>>>> + chan->jz_chan = jz4740_dma_request(chan, NULL);
>>>>>> + if (!chan->jz_chan)
>>>>>> + return -EBUSY;
>>>>>> +
>>>>>> + jz4740_dma_set_complete_cb(chan->jz_chan,
>>>>>> jz4740_dma_complete_cb);
>>>>>> +
>>>>>> + return 0;
>>>>> Zero is not expected value, you need to return the descriptors allocated
>>>>> sucessfully.
>>>>
>>>> Well, zero descriptors have been allocated. As far as I can see only a
>>>> negative
>>>> return value is treated as an error. Also the core doesn't seem to use the
>>>> return value for anything else but checking if it is an error.
>>> This is the API defination
>>> * @device_alloc_chan_resources: allocate resources and return the
>>> * number of allocated descriptors
>>>
>>
>> But 0 is still the number of descriptors that have been pre-allocated.
> and that should change, typically the driver will preallocate a pool of
> descriptors. These are to be used later for .device_prep_xxx calls.
>
Since the size of the descriptor is not know in advance this is not possible.
- Lars